"O Shakespeare! Shakespeare!" exclaims Lélio in The Return to Life, Berlioz's curious sequel to the Symphonie Fantastique, "how dazzling the impression your genius creates!" In his journal, the composer exclaims, with even less reservation: "Thou alone art the God worthy of artists." Like many of his contemporaries, he had been overwhelmed by his first experience of the plays on stage in English in 1827 and 1828, when a hastily assembled ad hoc company, comprising some of the greatest actors of the day, had performed Romeo and Juliet, Hamlet, Lear, and Othello at the Odéon Theatre in Paris.

Kemble was too old for Hamlet and Edmund Kean somewhat the worse for wear; the Lear was a comic hopelessly out of his depth, and though Macready did better with his impressive Othello, it was a hitherto undistinguished young Irish actress called Harriet Smithson in the roles of Ophelia and Juliet who swept all before her, establishing Shakespeare as an overwhelming force. Berlioz fell desperately in love with both of them, unrelentingly badgering Smithson into marrying him. The marriage ended disastrously, but his relationship with Shakespeare proved rather more durable. However uneven the standards of the English visitors, and however bastardised the texts they played - using the standard 17th and 18th-century bowdlerisations and rewritten endings - they were a revelation to their audiences, suggesting an approach to theatre, and perhaps to life itself, that set the upcoming generation of young French Romantics on fire.

From as early as the end of the 17th century, English-speaking French writers were nervously aware of the existence of this startling body of work. However, they still basked in the conviction that French art and literature (with theatre as a special glory) was the apogee of civilisation and viewed Shakespeare with superior fascination and fastidious selectivity, as if gazing out from their palaces over a distant jungle in which they were able to discern brilliant colours, exciting new species, huge but uncontrolled vitality.

They turned back to their own exquisitely cultivated gardens, wondering how it might be possible to tame this tropical outgrowth so that it might become useful and edifying as well as simply amazing, only to realise that the jungle was advancing, and in their direction. With great clarity, John Pemble charts the crisis in French life precipitated by the traumatic discovery that Anglo-Saxon culture was poised to displace the Gallic dispensation. As he puts it, in one of the elegant epigrams which pepper his text, "Until the Romantic era, the apostles of taste were defending preferences they believed to be universal. Thereafter, they were defending preferences they believed to be French." And Shakespeare was the advance guard of the marauding hordes. In his work the principles of order, structure, taste - the strict rules, derived, as they imagined, from the Greeks, by which Corneille, Racine and Molière had written their plays - were flouted, emotion and action were flagrantly indulged and life was presented in all its rough and often vulgar reality. And yet he was inarguably a genius.

For at least a century, he had been studied and, up to a point, appreciated, in literary circles, while being a byword for a dangerous primitiveness, an unwholesome barbarism, profoundly antipathetic, it was felt, to the French temperament, and indeed the French language. Le Tourneur's great edition of 1778 attracted 2,000 subscribers and the patronage of Louis XVI, but it was a curiously watered-down affair. Anything approaching accurate and complete translation was deemed not only impossible, but also inadvisable, carrying great potential for the corruption of French hearts and minds (and, perhaps even more worryingly, of the French language).

The Anglomania which Voltaire, Montesquieu and the Abbé Prévost had fostered in the early 18th century had drawn the line at what the arbiters of taste saw as Shakespeare's faults; it was Voltaire, that remarkable figure so heartily despised by his British contemporaries, who led both the French discovery of Shakespeare and the French denunciation of him. The English writer, he said, was overflowing with genius, "a genius full of strength and fecundity, of naturalness and sublimity, without the tiniest particle of good taste". (It was precisely this, of course, that recommended him to Berlioz, Dumas, Hugo et al.) At first, the approach was to regret respectfully that despite his greatness as poet and philosopher, he was uncouth and unskilled as a dramatist, the representative of an earlier age, ignorant of the refinements with which the Enlightenment had blessed mankind.

The rediscovery of the Renaissance put paid to this line of argument, when it became clear that Shakespeare was working within the tradition of Rabelais, Cervantes, Luther and Galileo, and was among its greatest ornaments, "steeped in continental humanism, poised between the old and the new", as Pemble says. In him, observed the critic Philarète Chasles in a marvellously perceptive phrase, "the mysterious echo of the Middle Ages mingles with the embryonic stirrings of ideas that would change the world." Another French critic, Brugière, claimed that Hamlet embodied the Renaissance's new burgeoning of the human spirit.

Pemble's constantly stimulating new book starts and ends with Voltaire; in between it covers a remarkably varied terrain, illuminating much more than its title might suggest. It goes without saying that he tells us a great deal about France, its psychology, its language, and its theatre; an unlooked-for bonus is the brilliant light he throws on Shakespeare, who so obstinately refused to accord with l'ésprit Français. It was something, they thought, to do with his sheer Englishness, coming as he did from the land of fog and the Bible, so very different from the sharp clarity of the French climate and its elegant ratiocinative procedures. The fog, particularly, was held responsible for the wildness, the violence and the emotionalism of the English, and their lamentable lack of propriety. Never mind country matters; as late as the 1840s, translators found it unacceptable to expose their audiences to the naming of certain unglamorous body parts: Othello's thigh, for example, in the phrase "I have a weapon / A better never did itself sustain / Upon a soldier's thigh" was inadmissible, and became a soldier's hand. The handkerchief upon which the plot hinges was held to be intolerably banal, and the French stage was not allowed to know that it was embroidered with anything as ordinary as strawberries until 1925.

In his translation of the complete works, Victor Hugo's son, François-Victor, finally unmuzzled Shakespeare, as his father said, revealing the full scatological horror of his language, though the translation's serviceable prose was unable to suggest the multifariousness of the original, or the way in which it developed over the 37 plays. The French language - with its "incorruptible syntax" - simply resisted it. But whatever the intellectuals thought, by now Shakespeare's popularity on the French stage was unstoppable, far eclipsing that of Racine or Corneille, even though the versions seen by the public often bore slight resemblance to what Shakespeare actually wrote (the version of King Lear that played at the Comédie-Française until late in the 19th century involved a love-affair between Cordelia and Edgar, and included the characters Alberic, Norclète and Frédegonde). Perhaps it would be truer to say that the idea of Shakespeare - boldly theatrical, admitting the whole range of human experience - had triumphed, rather than Shakespeare itself.

The plays, in increasingly accurate form, were central to the French theatre of the 20th century, seized on by every new movement as the perfect conduit for its ideas, but also to French literature; Pemble quotes Aragon's moving poem "Richard II Quarante", written after the fall of France, in which the poet compares himself with the deposed king, "more unfortunate than misfortune / Who remained king of his griefs". Pemble ranges deep and wide in his examination of the vexed but profoundly nourishing encounter of the French with Shakespeare. Sometimes he ranges perhaps a little too far - whole pages go by without so much as a mention of Shakespeare, as postmodernism, for example, is exhaustively defined - but his exposition of Shakespeare's strangeness to the French forces us to suspend our easy familiarity with him and experience something of the shock of his originality. Pemble has written one of the most interesting recent books in a bewilderingly overcrowded field.